20% of World's Plant Species Threatened With Extinction - Yes, Human Activity is Main Cause

Far and away, tropical rainforests were found to have the highest percentage of plant species at risk of extinction. Photo: tata_aka_T via flickr.

When you here the phrase 'endangered species' undoubtedly the cute, cuddly and carnivorous pop to mind, but according to new global analysis by The Royal Botanic Gardens, Kew, London's Natural History Museum and the IUCN shows that one in five of the world's plant species are threatened with extinction--in other words, about 76,000 of the world's estimated 380,000 species of plants have difficult times ahead.

About one third of the species (33%) in the sample are insufficiently known to carry out a conservation assessment. This demonstrates the scale of the task facing botanists and conservation scientists -- many plants are so poorly known that we still don't know if they are endangered or not.

Of almost 4,000 species that have been carefully assessed, over one fifth (22%) are classed as Threatened

Plants are more threatened than birds, as threatened as mammals and less threatened than amphibians or corals.

Gymnosperms (the plant group including conifers and cycads) are the most threatened group.

The most threatened habitat is tropical rain forest.

Most threatened plant species are found in the tropics.

The most threatening process is man-induced habitat loss, mostly the conversion of natural habitats for agriculture or livestock use.

Take that last bullet point in again. As with animal species threatened with extinction, the main problem is the scale of human activity being so large at present that it is pushing extinction rates to previously unseen levels, hundreds of time the historical rate of species extinction.

Breakdown of the differing level of threat faced by plant species. More info and further charts on the different plant groups: RBG Kew

In its press release, Professor Stephen Hopper, director of The Royal Botanic Gardens, Kew sums up the importance of the work: "For the first time we have a clear global picture of extinction risk to the world's known plants. This report shows the most urgent threats and the most threatened regions. In order to answer crucial questions like how fast are we losing species and why, and what we can do about it, we need to establish a baseline so that we have something against which to measure change. The Sampled Red List Index for Plants does exactly that."